Current Limited Load Switch
Functional Block Diagram
AAT4610A
IN
OUT
Under-
Voltage
Lockout
Over-Temperature
Protection
ON (ON)
1.2V
Reference
Current
Limit
SET
R
SET
GND
Ω
Application Information
Setting Current Limit
In most applications, the variation in I
LIM
must be
taken into account when determining R
SET.
The I
LIM
variation is due to processing variations from part
to part, as well as variations in the voltages at IN
and OUT, plus the operating temperature. See
charts "Current Limit vs. Temperature" and "Output
Current vs. V
OUT
." Together, these three factors
add up to a ±25% tolerance (see I
LIM
specification
in Electrical Characteristics section). Figure 1 illus-
trates a cold device with a statistically higher cur-
rent limit and a hot device with a statistically lower
current limit, both with R
SET
equal to 10.5kΩ. While
the chart, "R
SET
vs. I
LIM
" indicates an I
LIM
of 0.7A
with an R
SET
of 10.5kΩ, this figure shows that the
actual current limit will be at least 0.525A and no
greater than 0.880A.
I
LIM
(A)
1.2
1
0.88A
Device with high current limit at -40°C
0.8
0.6
0.4
0.525A
Device with low current limit at 85°C
0.2
0
0
1
2
3
4
5
V
OUT
(V)
Ω
Figure 1: Current Limit Using 10.5kΩ.
To determine R
SET,
start with the maximum current
drawn by the load and multiply it by 1.33 (typical
I
LIM
= minimum I
LIM
/ 0.75). This is the typical cur-
rent limit value. Next, refer to "R
SET
vs. I
LIM
" and
find the R
SET
that corresponds to the typical current
limit value. Choose the largest resistor available
that is less than or equal to it. For greater precision,
the value of R
SET
may also be calculated using the
8
4610A.2006.9.1.3
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
